Full coverage of a second generation (2G) or third generation network (3G) network, such as Global System for Mobile Communications (GSM) or Wideband Code Division Multiple Access (WCDMA), has been basically implemented.
With development of network technologies such as System Architecture Evolution (SAE) and Long Term Evolution (LTE) in a fourth generation network (4G) network, and with development of an enhanced high speed uplink packet access (HSPA) technology, a high speed downlink packet access (HSPA+) technology, and a worldwide interoperability for microwave access (WiMax) network technology, LTE networks or enhanced 3G networks have covered some urban areas and traffic hotspot areas. Therefore, in current communications networks, the LTE networks and the enhanced 3G networks coexist with a 2G or 3G network.
In 2G and 3G networks, a circuit switched (CS) domain is used to bear a conversational service such as a voice call, but in an LTE network and an enhanced 3G network, a packet switched (PS) domain is used to bear a conversational service.
Circuit switched fallback (CSFB) refers to fallback of user equipment (UE) covered by LTE to a CS domain network when the UE processes a voice service, so as to process the voice service in the CS domain network, thereby fulfilling an objective of reusing an existing CS domain device to provide a traditional voice service for a user in an LTE network.
When a user initiates an emergency session and the circuit switched fallback occurs, emergency call indication information needs to be carried, and a network needs to quickly select an emergency center according to location information of the user and then quickly set up an emergency call.
When the UE initiates an emergency call, an MSC (mobile switching center) receives the location information RNC ID of the user forwarded by an MME (mobility management entity), and selects an emergency center by using the RNC ID. However, because of a relatively large range of the RNC ID, there may be multiple emergency centers. Consequently, the MSC cannot quickly select an appropriate emergency center, and cannot quickly set up an emergency call, which leads to poor user experience.